Abnormalities of muscle tonus caused by neuromuscular diseases are classified into spasticity and rigidity: the former is a pyramidal tract sign and the latter is an extrapyramidal sign. To detect the degree of those is quite important in neurological examination. However, it is difficult to evaluate the degree accurately unless a neurologist is experienced. Although the Modified Ashworth Scale for spasticity and the UPDRS (Unified Parkinson Disease Rating Scale) for muscle rigidity are known as evaluation indices that currently are used often in clinical trial, the criteria of both of them are semi-quantitative, and thus differences may arise between evaluators and with the same evaluator. Accordingly, the development of quantitative measuring devices for these is desired.
Patent Document 1 recites a muscle tonus measuring apparatus that causes the elbow joint of a subject to undergo passive flexion and extension movement, obtains an elastic coefficient for the elbow joint from the relationship between joint angle and joint torque, and measures the surface myoelectric potential of the biceps brachii muscle and the triceps brachii muscle at the same time. Patent Document 1 recites that a feature amount extracted from the elastic coefficient of the elbow joint and the surface myoelectric potentials is useful in identifying the severity of muscle rigidity in Parkinson's disease patients, and that a feature amount extracted from the surface myoelectric potential of the biceps brachii muscle is useful in distinguishing between a healthy subject and a Parkinson's disease patient.